In assembling individual motion picture (i.e., film or video) scenes into larger compositions, the scenes are linked together by transitions. Most transitions are simple cuts, but a significant number are other forms of gradual transitions. These include dissolves (or cross-fades), wipes, and various specialized transitions such as blends, rotations and peels.
In a dissolve, a first scene is gradually dimmed while a second scene is gradually brightened, so that the viewer sees the transition as a continuous shift from the first scene to the second scene. During all of the types of gradual transition effect, as the term is to be understood in the context of this application, the first scene and second are both visible to some extent at the same time. For example, in a wipe, part of the second scene is displayed in a portion of the first scene, and this portion is gradually made larger until the second scene occupies the entire display area.
Preparing gradual transitions using 35 mm motion picture film is generally performed by specialized laboratories. 16 mm transitions are prepared using a technique called A-B rolling, in which two prints of the film are prepared with alternating scenes and then combined to yield the gradual transitions. Both of these techniques usually require the film to be conveyed to a processing laboratory in order to generate the transition in final form.
Video editing and composition systems also allow for the creation of transitions. In these systems, it is known to specify a gradual transition by its centerpoint. By centerpoint is meant the point in time within the transition half way between the beginning and end of the transition. The editor manipulates the transition much like a cut, but upon playback, the transition begins before the centerpoint, and ends after the centerpoint. The user may also manually generate the transition using an effects bar control, which is a control lever that often resembles a joystick. This allows the user to control the rate at which the transition takes place. These manually-generated transition profiles may also be stored.
It is also known to display a series of independent monitors with the material from the first scene above a second series of independent monitors with the material from the second scene. In the top row, each monitor shows a successive frame of the first scene, and in the bottom row, each monitor shows a corresponding successive frame of the second scene. This system may allow the user to view several frames from each scene in a transition simultaneously. The Montage Picture Processor system, available from Montage R&D Corp. of Littleton, Mass. uses this approach.